It is becoming increasingly popular to use electronic personal organiser equipment for managing appointments. In addition to dedicated personal organisers, which are usually in a palmtop format, personal organisation functions have been provided in mobile phones, wristwatches and software for personal computers. Personal organisers usually include a diary/calendar whereby a user may enter the time and date of an appointment together with details of the appointment such as its location and purpose. Many personal organisers are able to remind a user at the time of an appointment, or at a set time beforehand. The reminder could take the form of an audible alarm or another alerting format such as flashing of an indicator light or vibration.
It can be difficult for a user to obtain appropriate reminders from such a conventional diary/calendar because the time at which a reminder should ideally be given is dependant on the amount of time the user needs to reach the appointment. One approach is for the organiser to remind a user of an appointment at the very time of the appointment. However, if the user is not already at the location of the appointment when the reminder is issued then the reminder is likely to have come too late to allow the user to reach the appointment on time; alternatively, if the user has already got to the appointment by the time the reminder issues then his appointment may be unwantedly interrupted by the reminder. Another approach is to have the personal organiser equipment generate a reminder a set time in advance of the appointment. However, this requires the user to configure the equipment to generate such reminders, and since they are issued at a fixed timer before the appointment the advance reminder-s are unlikely to be at an appropriate time to cause the user to travel efficiently to his appointment. In addition, the effectiveness of the personal organiser, and its popularity with a user, is diminished by it issuing inappropriate alerts.
Separately from personal organiser technology, apparatus exists for determining a user's location. Systems for determining location include satellite location systems such as GPS (global positioning system) and cellular radio location systems, for example making use of measurement of timing differences between nearby basestations. In the GPS system a receiver determines its location by means of signals received from earth-orbiting satellites. It is also possible for a mobile station in a cellular telephone network or the like to determine its location (or for the network to determine its location) by means of timing delays of signals to or from respective base-stations or by other means.